1. Field of the Invention
The present invention relates to manually operable two-wheeled hand trucks and in particular to a hand truck which is provided with a pair of curved gripping extensions for engaging, said gripping extensions attached to a means for spreading said gripping extensions horizontally to a desired distance apart without rotation of the gripping extensions about a pivot. The gripping extensions may be spread to a desired distance apart by a hand crank located on a side of the truck frame.
2. Description of the Prior Art
The handling and moving of stacked tires in a warehouse setting is a tedious and cumbersome task using commonly available two-wheeled hand trucks. The prior art hand trucks most commonly in use are those having a stationary mounted gripping extension(s) which is/are adapted to be slid under the object or objects to be transported. The object or stack of objects must be tilted away from the hand truck in order for the gripping extension to be positioned between the bottom of the object or objects and the floor. Thus, two people are often required to load the objects onto the truck.
When moving a stack of tires, however, prior art hand trucks with a single stationary mounted gripping extension or toe are impractical for several reasons. First, the prior art trucks with a single stationary toe only provide a nominal support surface. Specifically, they do not readily permit the adjusting of the alignment of the tires, nor do they provide a sufficient grasping force toward the front of the tires to give a lifting force to the entire stack to prevent buckling or collapsing of the stack of tires. Additionally, since most car and truck tires range in size from roughly 20 to 34 inches in diameter, it is difficult for one size hand truck to accommodate all sizes and still provide a means to move each size stack of tires in an orderly fashion. Examples of such prior art hand trucks with a single stationary gripping extension can be found in U.S. Pat. Nos. 1,201,957; 3,642,301; 4,114,771; and 4,226,434 herein incorporated by reference.
Hand trucks having load engaging jaws which swing around vertical axes and in a horizontal plane during loading are known. Examples of this type of truck can be found in U.S. Pat. Nos. 1,551,928; 2,475,874; 2,485,545; and 3,084,820 incorporated herein by reference. However, a distinct disadvantage of using this type of hand truck is that the object or stacks of objects, for example stacks of tires, must be stacked some distance apart to give enough space on either side for the gripping extensions to swing horizontally and engage the object or objects. Additionally, the force used to move the gripping extensions in the horizontal position is exerted via a foot pedal connected to the gripping extensions by a series of rods and links, which tends to cause stiff and jerky movement of the gripping extensions, and with continued use, weakening of the connecting rods and links. Further, these prior art trucks fail to provide a means whereby the gripping extensions are prevented from further movement after the load is lifted, and the gripping extensions often shift causing the stack of tires to fall from the hand truck.
Another variation of this type of hand truck is found in U.S. Pat. No. 3,425,575 which discloses a truck wherein a pair of gripping extensions swing around horizontal axes and toward and away from each other along a vertically disposed arcuate path with respect to the floor surface. However, this type of hand truck also suffers from the disadvantages noted above.
Accordingly, it is an object of the present invention to provide a hand truck comprising a frame with a pair of curved gripping extensions attached at the base thereof, said gripping extensions capable of being spread in a horizontal plane without pivoting around vertical axes. The pair of gripping extensions may then be opened to a distance sufficient to insert between stacks of tires, with minimal space between the stacks, and can then be tightened about the stack for moving. The truck of the present invention also provides a means whereby the gripping extensions are prohibited from further movement after a stack of tires is lifted, thereby providing greater stability in transport.
Another object of the present invention is to provide a hand truck with a means for spreading a pair of gripping extensions attached to the frame of said hand truck, said means comprised of a sprocket and link chain mechanism which is turned by a hand crank on a side of the truck frame. This sprocket and link chain mechanism provides a smooth and easy way for said gripping extensions to be adjusted to fit tires of various diameter.
A further object of the present invention is to provide a mechanism for spreading or adjusting the distance between gripping extensions on a hand truck comprised of a threaded drive screw bar in the base of said hand truck, said bar comprised of a left threaded screw on one half and a right threaded screw on the other half, with a floating nut on each left and right threaded half, said nut containing extensions capable of engaging and moving said gripping extensions upon axial rotation of said threaded drive screw bar.